The public debate on whether the United States and other countries are able to prevent Iran from obtaining a nuclear weapon exhausted itself years ago.

Yet, discussion about confrontation with Iran will persist until one of two things happens: Tehran provides sufficient transparency over its suspected nuclear weapons activities to meet the demands of the International Atomic Energy Agency (IAEA), Tel Aviv, and Washington; or Israel and/or the United States attacks Iran’s nuclear facilities.

Unless the major players are bluffing and ultimately back down—which has happened before—one of these determining actions will likely take place within the next two years.

If President Obama—or any future occupant of the White House—does decide to attack Iran, there is an important prerequisite that has remained largely unexplored: How would the president sell the war to the American people?

The president wouldn’t have to start from scratch. Iran has been demonized by the United States since the nascent Islamic Republic seized the U.S. embassy compound in Tehran and held fifty-two hostages from November 1979 to January 1981.

Since then, polling has consistently demonstrated two strong beliefs: Americans do not like and are afraid of Iran. A recent Gallup poll found that 87 percent of Americans held an “unfavorable” opinion of Iran, a number that hasn’t changed in decades.

In addition, in a September 2011 survey asking, “Which country is the greatest threat to the United States?” 63 percent of respondents listed Iran first or second. (In June 2009, 79 percent of respondents believed Iran to be a “very serious” or “moderately serious” threat to the United States.)

Despite the polling numbers, Americans are largely split over a U.S. military attack on Iran (support ranges from 41 to 56 percent) and there is broad approval for stronger economic sanctions and diplomatic action. Interestingly, the action favored by most Americans (81 percent), “direct diplomatic talks between the United States and Iran,” is not part of the Obama administration’s strategy.

In addition to the lukewarm support among Americans for attacking Iran, President Obama or his successor would also have to tackle two problematic assessments from the U.S Intelligence Community (IC).

First, as Director of National Intelligence James Clapper has repeatedly reaffirmed since late January, “we don’t believe they’ve actually made the decision to go ahead with a nuclear weapon.” Just yesterday, James Risen reported in the New York Timesthat the IC continues to believe (based on an assessment first made in November 2007) that Iranian Supreme Leader Ayatollah Ali Khamenei halted his country’s nuclear weapons activities in 2003.

This might be hard for many to grasp, since polling has found the American people disagree with the collective judgment of the 210,000 civilian and military employees and 30,000 private contractors comprising the IC. A recent poll found that 84 percent of Americans think Iran is developing nuclear weapons, while another from February 2010 concluded that 71 percent of Americans believe that Iran currently has nuclear weapons.

Second, Lieutenant General Ronald Burgess, chief of the Defense Intelligence Agency (DIA) told the Senate Armed Services Committee in February that, despite all of Iran’s threats, “it is unlikely to initiate or intentionally provoke a conflict or launch a preemptive attack.” This assessment is undoubtedly difficult for some to reconcile with the rhetorical bluster of senior Iranian officials, including repeated threats to close the Strait of Hormuz if U.S. aircraft carriers entered the waterway.

In February, however, the USS Abraham Lincoln steamed through the strait without incident. In fact, Chief of Naval Operations Admiral Jonathan Greenert told reporters that Iran’s naval forces have not responded with increased activity, adding: “The Iranian navy has been unto itself professional and courteous.” This confirms what U.S. Navy officials have told me in private conversations: for the past two decades, the U.S. and Iranian navies have carefully avoided direct confrontations, and routinely cooperate on a tactical level to rescue distressed ships or lost seafarers.

To build up support for a preemptive attack, the U.S. president could play to the widely-held conviction that Tehran is nearing—or crossed—the nuclear threshold, but he will also need to explain why the intelligence professionals, on the receiving end of over $75 billion in taxpayer funds, are wrong.

Presidents sell wars by offering a buffet of justifications in the hopes that citizens of varied beliefs and opinions will find something to sink their teeth into. If you are old enough, you may recall the multiple explications provided by senior officials for the use of military force in Iraq from 1991 to 2011, Bosnia from 1992 to 1995, Kosovo in 1999, or even in Libya last year; justifications included to protect civilians, overthrow regimes, send a “message” to other dictators, and repay European allies for support in Afghanistan.

The media circus surrounding the Iranian nuclear program has distorted the underlying rationale for any use of force. The United States must not attack Iran without clearly defined strategic objectives, a clear understanding of how attacking its suspected nuclear weapons facilities will advance those objectives, and a theory of victory for how those facilities could be destroyed at an acceptable level of cost. So far, both proponents of attacking Iran and the president have avoided addressing these three concerns with any clarity.